Are there any issues with using Niceforms?

Answer 1

The only issue in my opinion with any of these types of techniques is if the form relies upon the technique to function.

From looking at their demo page:

• With JavaScript disabled, the form still looks pretty much the same except for the nice styling for the actual form elements. The form still functions.
• With CSS and JavaScript disabled, the form is still usable and functions.

One potential issue I can see with them is if you have to support IE6 with the full styling. Of course - if you have that requirement, you have more problems than just this.